Summary
The monitoring of induced seismicity is a common operation in many industrial activities, such as conventional and non-conventional hydrocarbon production or mining and geothermal energy ...exploitation, to cite a few. During such operations, we generally collect very large and strongly noise-contaminated data sets that require robust and automated analysis procedures. Induced seismicity data sets are often characterized by sequences of multiple events with short interevent times or overlapping events; in these cases, pick-based location methods may struggle to correctly assign picks to phases and events, and errors can lead to missed detections and/or reduced location resolution and incorrect magnitudes, which can have significant consequences if real-time seismicity information are used for risk assessment frameworks. To overcome these issues, different waveform-based methods for the detection and location of microseismicity have been proposed. The main advantages of waveform-based methods is that they appear to perform better and can simultaneously detect and locate seismic events providing high-quality locations in a single step, while the main disadvantage is that they are computationally expensive. Although these methods have been applied to different induced seismicity data sets, an extensive comparison with sophisticated pick-based detection methods is still missing. In this work, we introduce our improved waveform-based detector and we compare its performance with two pick-based detectors implemented within the SeiscomP3 software suite. We test the performance of these three approaches with both synthetic and real data sets related to the induced seismicity sequence at the deep geothermal project in the vicinity of the city of St. Gallen, Switzerland.
Earthquake early warning would be improved if the final size of an ongoing earthquake could be predicted early in the rupture process. Previous research relies largely on parameters derived from ...seismic waveforms, resulting in widely varied estimates of how much of the rupture must be complete before final sizes can be predicted. We demonstrate here that incorporating prior information on along‐strike variation in source fault structural maturity helps improve constraints on the earthquake's final size. Using surface slip profiles from 26 large continental earthquakes worldwide, we derive a generic empirical relation between earthquake slip, rupture length, and along‐strike variability in source fault maturity. Using this equation, we fit successive slip profiles developing during each earthquake and find that, on average, we predict the final length and magnitude of an earthquake once it has reached ~20% of its total length. Our findings thus demonstrate a clear determinism in the rupture process.
Plain Language Summary
When an earthquake initiates, an important question is whether and when we can anticipate what its final size will be. Previous studies have searched the answer to this question in seismic data from the earthquake alone. Here we suggest that we should incorporate additional information on the tectonic source fault that is rupturing. Based on earthquake slip‐length functions measured at the ground surface, we develop a generic empirical equation between earthquake slip, rupture length, and along‐strike changes in source fault structural maturity, for continental earthquakes. We show that applying this relationship to evolving earthquake slip profiles improves how quickly earthquake length and magnitude can be determined. These findings demonstrate that part of the rupture process is controlled by the physical properties of the source faults and may have important implications for earthquake early warning.
Key Points
We parameterize a generic relationship between along‐strike fault maturity, coseismic slip, and final rupture length
Using fault maturity as a prior improves earthquake magnitude and rupture length predictions as needed for earthquake early warning
We predict final length and magnitude once earthquake rupture has reached ~20% of its total length, what shows a clear determinism in the rupture process
SUMMARY
To provide rapid estimates of fault rupture extent during large earthquakes, we have developed the Finite Fault Rupture Detector algorithm, ‘FinDer’. FinDer uses image recognition techniques ...to detect automatically surface‐projected fault ruptures in real‐time (assuming a line source) by estimating their current centroid position, length L, and strike θ. The approach is based on a rapid high‐frequency near/far‐source classification of ground motion amplitudes in a dense seismic network (station spacing <50 km), and comparison with a set of pre‐calculated templates using ‘Matching by Correlation’. To increase computational efficiency, we perform the correlation in the wavenumber domain. FinDer keeps track of the current dimensions of a rupture in progress. Errors in L are typically on the same order as station spacing in the network. The continuously updated estimates of source geometries as provided by FinDer make predicted shaking intensities more accurate and thus more useful for earthquake early warning, ShakeMaps, and related products. The applicability of the algorithm is demonstrated for several recorded and simulated earthquakes with different focal mechanisms, including the 2009 Mw 6.3 L’Aquila (Italy), the 1999 Mw 7.6 ChiChi (Taiwan) and the Mw 7.8 ShakeOut scenario earthquake on the southern San Andreas Fault (California).
Earthquake early warning systems (EEWSs) aim to rapidly detect earthquakes and provide timely alerts, so that users can take protective actions prior to the onset of strong ground shaking. The ...promise and limitations of EEWSs have both been widely debated. On one hand, an operational EEWS could mitigate earthquake damage by triggering potentially cost- and life-saving actions. These range from automated system responses such as slowing down trains to the actions of individuals that receive the alerts and take protective measures. On the other hand, the effectiveness of an EEWS is conditional on the ability to issue warnings that are sufficiently accurate and timely to facilitate an appropriate action. The refinement of earthquake early warning (EEW) algorithms and the installation of denser and faster seismic networks have improved performance; however, the benefit in risk reduction that an EEWS could achieve remains unquantified. In this study, we leverage upon regional event-based probabilistic seismic risk assessment to devise a quantitative and fully customizable framework for evaluating the effectiveness of EEW in mitigating seismic risk. We demonstrate this framework using Switzerland as a testbed, for which we compute and contrast human loss exceedance curves with and without EEW.
The Swiss Seismological Service (SED) at ETH has been developing methods and open-source software for Earthquake Early Warning (EEW) for more than a decade and has been using SeisComP for earthquake ...monitoring since 2012. The SED has built a comprehensive set of SeisComP modules that can provide EEW solutions in a quick and transparent manner by any seismic service operating SeisComP. To date, implementations of the Virtual Seismologist (VS) and Finite-Fault Rupture Detector (FinDer) EEW algorithms are available. VS provides rapid EEW magnitudes building on existing SeisComP detection and location modules for point-source origins. FinDer matches growing patterns of observed high-frequency seismic acceleration amplitudes with modeled templates to identify rupture extent, and hence can infer on-going finite-fault rupture in real-time. Together these methods can provide EEW for all event dimensions from moderate to great, if a high quality, EEW-ready, seismic network is available. In this paper, we benchmark the performance of this SeisComP-based EEW system using recent seismicity in Switzerland. Both algorithms are observed to be similarly fast and can often produce first EEW alerts within 4–6 s of origin time. In real time performance, the median delay for the first VS alert is 8.7 s after origin time (56 earthquakes since 2014, from M2.7 to M4.6), and 7 s for FinDer (10 earthquakes since 2017, from M2.7 to M4.3). The median value for the travel time of the P waves from event origin to the fourth station accounts for 3.5 s of delay; with an additional 1.4 s for real-time data sample delays. We demonstrate that operating two independent algorithms provides redundancy and tolerance to failures of a single algorithm. This is documented with the case of a moderate M3.9 event that occured seconds after a quarry blast, where picks from both events produced a 4 s delay in the pick-based VS, while FinDer performed as expected. Operating on the Swiss Seismic Network, that is being continuously optimised for EEW, the SED-ETHZ SeisComP EEW system is achieving performance that is comparable to operational EEW systems around the world.
The InSight mission (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) has been collecting high-quality seismic data from Mars since February 2019, shortly after its ...landing. The Marsquake Service (MQS) is the team responsible for the prompt review of all seismic data recorded by the InSight's seismometer (SEIS), marsquake event detection, and curating seismicity catalogues. Until sol 1011 (end of September 2021), MQS have identified 951 marsquakes that we interpret to occur at regional and teleseismic distances, and 1062 very short duration events that are most likely generated by local thermal stresses nearby the SEIS package. Here, we summarize the seismic data collected until sol 1011, version 9 of the InSight seismicity catalogue. We focus on the significant seismicity that occurred after sol 478, the end date of version 3, the last catalogue described in a dedicated paper. In this new period, almost a full Martian year of new data has been collected, allowing us to observe seasonal variations in seismicity that are largely driven by strong changes in atmospheric noise that couples into the seismic signal. Further, the largest, closest and most distant events have been identified, and the number of fully located events has increased from 3 to 7. In addition to the new seismicity, we document improvements in the catalogue that include the adoption of InSight-calibrated Martian models and magnitude scales, the inclusion of additional seismic body-wave phases, and first focal mechanism solutions for three of the regional marsquakes at distances ∼30°.
•The V9 catalogue includes 951 events, of which 486 are new since the previous report.•Multiple large marsquakes with MWMa 4.0–4.2 were recorded.•Some new events are within 100 km of the lander and beyond the core shadow which were not seen before.•Four events are located close to the lander, which include chirps and are interpreted as meteorite impacts.•The catalogue also includes 1062 very local events that may be due to thermal stresses.
Earthquake Early Warning (EEW) systems can trigger actions just before the shaking hits and hence mitigate the impact of damaging earthquakes. Recent studies have mainly focused on technical ...challenges, performance or on the attitudes of the public towards EEW systems in countries where EEW systems are already in operation or where damaging earthquakes are frequent. Building on these efforts, from the societal perspective we assess how different message elements influence the intention to take action and ability to grasp relevant information within a few seconds. Further, we explore the public attitudes towards EEW systems in a country where damaging earthquakes are expected less frequently. In a survey (N = 596, between-subjects experiment) targeting the Swiss public, we assess EEW system preferences and test different versions of EEW messages to identify elements which trigger people to take immediate actions and can be correctly recalled. Our main findings are that i) the public attitudes in countries with moderate seismic hazard are similar to attitudes in countries with high seismic hazard; ii) pictograms trigger people to protect themselves on the spot whereas maps prompt the public to look for further information or to warn others; iii) the designs preferred by the public are not always those that actually trigger them to take action; and iv) people tend to react proportionally to the hazard level. We show that insights from studies focusing on societal issues related to EEW systems can help operators define technical settings and to address specific concerns or likely misconceptions in education campaigns.
•Public perception of EEW in a country with moderate seismic hazard.•Swiss public's preferences for EEW are similar to the preferences in other countries.•The EEW message design influences people's intentions to take action.•What people like best is not necessarily what helps them to take action.•EEW messages with pictograms trigger people most to take protective actions.
Earthquake early warning (EEW) not only improves resilience against the risk of earthquake disasters, but also provides new insights into seismological processes. The
Fin
ite-Fault Rupture
De
tecto
r
...(FinDer) is an efficient algorithm to retrieve line-source models of an ongoing earthquake from seismic real-time data. In this study, we test the performance of FinDer in the Sichuan-Yunnan region (98.5
o
E–106.0
o
E, 22.0
o
N–34.0
o
N) of China for two datasets: the first consists of seismic broadband and strong-motion records of 58 earthquakes with 5.0 ≤
M
S
≤ 8.0; the second comprises additional waveform simulations at sites where new stations will be deployed in the near future. We utilize observed waveforms to optimize the simulation approach to generate ground-motion time series. For both datasets the resulting FinDer line-source models agree well with the reported epicenters, focal mechanisms, and finite-source models, while they are computed faster compared to what traditional methods can achieve. Based on these outputs, we determine a theoretical relation that can predict for which magnitudes and station densities FinDer is expected to trigger, assuming that at least three neighboring stations must have recorded accelerations of 4.6 cm/s
2
or more. We find that FinDer likely triggers and sends out a report, if the average distance between the epicenter and the three closest stations,
D
epi
, is equal or smaller than log
10
(
M
a
+
b
) + c, where
a
= 1.91,
b
= 5.93, and
c
= 2.34 for
M = M
W
≥ 4.8, and
c
= 2.49 for
M = M
S
≥ 5.0, respectively. If the data used in this study had been available in real-time, 40–70% of sites experiencing seismic intensities of V-VIII (on both Chinese and MMI scales) and 20% experiencing IX-X could have been issued a warning 5–10 s before the
S-
wave arrives. Our offline tests provide a useful reference for the planned installation of FinDer in the nationwide EEW system of Chinese mainland.
The InSight mission will land a single seismic station on Mars in November 2018, and the resultant seismicity catalog will be a key component for studies aiming to understand the interior structure ...of the planet. Here, we present a preliminary version of the web services that will be used to distribute the event and station metadata in practice, employing synthetic seismograms generated for Mars using a catalog of expected seismicity. Our seismicity catalog consists of 120 events with double-couple source mechanisms only. We also provide Green’s functions databases for a total of 16 structural models, which are constructed to reflect one-dimensional thin (30 km) and thick (80 km) Martian crust with varying seismic wave speeds and densities, combined with two different profiles for temperature and composition for the mantle. Both the Green’s functions databases and the precomputed seismograms are accessible online. These new utilities allow the researchers to either download the precomputed synthetic waveforms directly, or produce customized data sets using any desired source mechanism and event distribution via our servers.
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